1. Field of the Invention
This invention relates to compositions and methods for the cosmetic treatment of substrates, particularly the surface of materials in the form of fibres or essentially flat structures. More particularly, the invention relates to the cosmetic treatment of substrates which, owing to the chemical nature of the material, present at their surface at least one species of nucleophilic group for chemical interaction with one or more cosmetic substances with which the material surface is to be treated. Such substrates include for example proteinaceous materials such as keratin, e.g., as found in hair, skin and nails and various animal body parts such as horns, hooves and feathers, and other naturally occurring protein containing materials, e.g., silk and saccharide-derived materials such as those derived from cellulose or cellulose derivatives e.g. natural products such as cotton. The invention is concerned particularly with the treatment of these kinds of substrates with substances which impart one or more tactile, visual or other cosmetic benefits.
2. The Related Art
It is well known and well documented in the relevant technical and patent literature that fibrous materials such as hair and fabrics or the like can be treated with cosmetic agents which deliver one or more desirable cosmetic benefits, for example, conditioning, setting or styling. Such treatment extends not only to fibrous materials, but also to materials which are substantially flat, like skin. Conventionally these treatments are carried out by applying to the surface of the material usually a composition containing the one or more active ingredients which serve to impart the benefit or benefits which are wanted. The application of such conventional cosmetic treatment compositions to achieve the desired results relies essentially on two key factors: firstly, it is important that the active ingredient or ingredients with which the substrate is to be treated are provided in a form of composition which on the one hand is stable upon storage and maintains the essential treatment agent or agents in cosmetically active form, and on the other hand allows the active(s) to be deposited from the composition onto the substrate surface, which deposition imparts the desired benefit to a sufficient degree and in an economical manner; secondly, it is essential that once deposited the cosmetic active or actives are retained on the substrate surface, so that when the treatment is completed and for example the substrate is rinsed to remove unwanted excess composition or residual components thereof, sufficient of the cosmetic active substance or substances remains bonded to the substrate surface so as to impart the intended characteristic cosmetic benefit or benefits thereto.
This bonding of active material to the treated substrate surface is generally of the nature of physisorption; that is to say, molecules of the cosmetic active(s) are absorbed onto the surface of the substrate by virtue of physical intermolecular forces such as hydrogen bonding. Conventionally, it has been accepted that this form of retention of active substances on treated substrate surfaces gives adequate results as regards achievable cosmetic benefits and economics, and this is perhaps an explanation of why efforts over recent years have been towards improving the technology of deposition itself as a means for improving the efficacy and economy of cosmetic products.
A major problem, however, associated with known cosmetic products, even those which employ advanced patented deposition systems, is that once a substrate has been treated with a cosmetic agent, because of the very nature of the physical forces which bond the active to the substrate material, retention of the cosmetic agent at the desired site of application is frequently short-lived. Most frequently, this temporary retention is brought about by the need for washing of for example the skin, hair, other fibres or other substrates which have been treated with the cosmetic active. Often particular cosmetic actives are applied to a substrate material in the first place during or immediately following a washing treatment, and so unless such cosmetic treatment is repeated at the time of each wash, any kind of performance or retention for a period in excess of a period between washes is difficult to achieve. Admittedly, over recent years there have been moves to use cosmetic treatment compositions and regimes which are milder and less harsh to hair, other fibres or skin or the like, but even so the act itself of washing to remove dirt and excess oils and so on generally also removes any valuable cosmetic agent which is wanted for retention to impart a particular benefit with some long lasting effect.
Not only does the above problem mean that the efforts in the art towards advanced deposition systems represent at best a partial solution to an overall underlying problem, but it also demonstrates the significant shortcomings of conventional cosmetic product technology with regard to inefficient, uneconomical use and waste of cosmetic raw materials. With recent public awareness leaning towards avoidance of environmental contaminants and possible risks to the health of animals and plants, a reduction in the amount of synthetic, frequently non-naturally degradable materials transported into the environment following use by human consumers would also be a welcome advance.
As relevant prior art to the present invention there may be mentioned EP-A-0392735 (Minnesota Mining and Manufacturing Company), which discloses certain azlactone-functional polymeric solid supports which are useful as complexing agents, catalysts, reagents, adsorbents, chromatographic supports and as biologically active supports for reaction with functional materials, one example of which is a protein, for example in protein synthesis. Whilst various polymer backbone species are disclosed for azlactone functionalisation in the formation of these polymeric supports, there is no disclosure or suggestion in the reference of the use of polymers which themselves may have a particular function which it may be desired to exploit.
EP-A-0435004 and EP-A-0437075 (both Dow Corning Corporation) describe, respectively, chlorobenzyl functionalised and acrylic-functionalised siloxanes for use in the permanent waving of hair. Such functionalised siloxanes are useful as replacements for oxidising agents which are used in conventional perming treatments to cross-link reduced sulphur-sulphur bonds in hair proteins. Both of these disclosures, however, fail to address the problem of temporary retention on the hair of cosmetic agents such as film-forming conditioning and bodying/setting materials, and relate only to the well-documented use in the literature of certain types of cross-linking agent for the specific use in the cross-linking of a reduced hair structure.
With the above criteria in mind, it was an object of the present invention to ameliorate at least some of the above mentioned problems and to devise a means for achieving improved levels of retention of cosmetic agents on treated substrate surfaces, such that a desired one or more cosmetic benefits wanted of a particular treatment can be achieved readily and with a significantly longer lasting effect than has hitherto been the case using conventional application and deposition technology.